1. Field
Apparatuses and methods consistent with exemplary embodiments relate to a cryptographic device.
2. Description of Related Art
In recent years, information transmitted by a user in communications using a smart card or an integrated circuit (IC) card, Internet communications, wireless local area network (LAN) communications, and Internet banking include secret information. Secret information may be leaked by hacking. Therefore, hardware encryption/decryption devices are increasingly being used to prevent the leakage of secret information. Prior to transmission of secret information receiving a signature or passing an authentication procedure, the hardware encryption/decryption device transforms the secret information into a cryptogram.
Because speed of an encryption operation is typically low, most encryption operations are carried out using hardware to be applied to devices such as a smart card. Data encryption standard (DES) is a type of block encryption algorithm and a symmetric key encryption scheme using 56 bits of a key. A substitution box (hereinafter referred to as “S-Box”) for use in DES carries out a substitution operation to convert an m-bit input into an n-bit output.
When DES is embodied with hardware, an S-Box is designed using a lookup table. However, a data value of the S-Box may be exposed to a hacker according to a hardware design technique. Accordingly, there is a need for the hardware design for an S-Box that is capable of preventing exposure of internal data even when the S-Box is attacked by a hacker.